1. Technical Field
The present invention relates to an optimization method for deposition time. More particularly, the present invention relates to an optimization method for deposition time in a thermal oxidization technique that is affected by a change in atmospheric pressure.
2. Related Art
Conventionally, thermal oxidation processing receives environmental influences such as atmospheric pressure at the time of processing and a change over time within an apparatus. Without correction with fine-tuning of oxidization time, poor processing such as an imbalanced thickness value results. In particular, atmospheric pressure change becomes a factor in fluctuating the characteristics of products in thin film processing. In addition, the following jobs have been performed in response to such influences and have different changes in each apparatus or job: a) whenever a worker processes a product, he or she writes down oxidation time and atmospheric pressure data at the time of processing; b) data of an immediately preceding processed lot of the same oxidation process is searched; c) current atmospheric pressure is examined and compared with the data described in b) (The data is input to a program for calculation only, and the next oxidization is calculated); and d) a worker inputs the calculated data of oxidation time into a thermal oxidation processing apparatus. In addition, a control method for the oxidation, which is a diffusion processing condition with atmospheric pressure, is disclosed. This technology automatically corrects oxidation time by atmospheric pressure data (see Japanese Patent Publication Laid-Open No. 5-32500 for example).
However, the conventional technology has the following problems.
The correction is completed only by atmospheric pressure, and there is no system that feeds back a value of an immediately preceding lot. Namely, there is no system of performing correction with high accuracy such as a feedback approach for the next oxidization time which considers the thickness result of the immediately preceding lot of the same oxidization process. In addition, the data input operation is manual and therefore it is possible to input inaccurate data. Also, it takes a great amount of time to observe atmospheric pressure data, as well as input and output data with manual handling. This results in poor operation efficiency.
In view of the above problems, the present invention is intended to a) calculate the optimum time for oxidization processing with a process management system based on atmospheric pressure data at the start (starting time) of processing, a target value of thickness in the process, data of oxidization time atmospheric pressure and thickness at the time of the immediately preceding process of the same oxidization processing job. Further, the invention is intended to b) directly download the calculated time for the oxidation process to a thermal oxidization apparatus via an on-line system and start product processing. c) Usually, a barometer is not installed in the thermal oxidation processing device such that atmospheric pressure data are delivered to a process management system from other semiconductor devices via on-line communication and used. d) Thickness data, oxidation time, and atmospheric pressure data are integrally processed by a process control system such that an immediately preceding lot processed from past data of the same oxidization processing job, thermal oxidization time, thickness data, and atmospheric pressure data related to the lot are retrieved. By performing the above a) to d), the present invention can provide an optimization method for deposition time that improves the uniformity of processing time for an oxidized thickness technique.